I have a 48" Lesco walk-behind (belt drive) with about 150 hrs on it. Model # 708682. My operator presence control/lever isn't working properly in multiple ways. When the blade is engaged, the left handle must be held down or the engine dies (holding the right one down without the left one down will not allow the engine to run). Also, I cannot leave the engine running with the transmission in neutral (blade off) or it will die. Seems like two separate issues? Any idea what part(s) I should replace? How can I temporarily bypass the safety mechanisms to prove out what exactly my issue is so I know what part to get? Many thanks in advance.